Spoiler Alert!When you enter that room, go around to the right behind the fallen pillars. There is an urn that has a Bush Ninja hiding behind it. Instead of killing him, you need to induce him to follow you so that HE stands on the button. As long as you face away from him, he'll creep along behind you. Once he stands on the button, he won't be able to get off. Then you can smash the urn behind the wall.
The other thing you need to find in that room is the more important in the scheme of the game, FWIW.